Methods for preparing stable emulsions are known. For example, incorporation of a surfactant into an emulsion is a widely used technique for stabilizing an emulsion. However, as there is a desire for preparing emulsions with decreased amounts of surfactant, in order to address both safety and environmental concerns, additional techniques have been proposed.
One such method utilizes amphiphilic polymers, but this technique is limited in that it is only useful in certain emulsions where the amphiphilic polymer is compatible with the oil phase of the emulsion, or where polymer interactions do not disrupt the rheological behavior of the emulsion. A second method utilizes particles, typically inorganic, to form a Pickering emulsion as known in the state of the art. This technique likewise has drawbacks in that the particles must be carefully chosen such that they are compatible with the oil phase of the emulsion and that the properties of the particles do not adversely affect the emulsion.
Microcapsule techniques have also been proposed. For instance, U.S. Pat. Nos. 6,159,453 and 6,238,650 describe sol-gel microcapsules comprising sunscreen active ingredients; U.S. Patent Publication No. 2008/199526 describes compositions comprising two sunscreen agents encapsulated within microcapsules having a specific diameter; and U.S. Pat. No. 8,110,284 describes microcapsules having a core material encapsulated within a microcapsular shell, wherein the core material comprises an active ingredient.
Additionally, U.S. Patent Publication Nos. 2011/158923, 2011/293677, and 2011/311723 all describe silica shell techniques. These techniques have a drawback, however, in that the shell is made by a process that releases harmful by-products, which for both human and environmental safety reasons, is desired to be avoided.
In addition to avoiding the above-mentioned drawbacks, there is also a desire in certain industries, such as, for example, the food, cosmetic, and consumer chemical (e.g. household product) industries, to prepare emulsions that have certain properties, such as the ability to concentrate/dilute dispersions in water or other emulsions without interaction, to prepare emulsions that are stable even after application to a surface and/or evaporation of the water phase, particularly at room temperature, and to prepare emulsions that have slow-release properties, for instance.
Thus, there is a need for methods to prepare O/W emulsions that provide the desired properties and which can be used in a variety of applications and industries, while decreasing the use of surfactants and increasing stability of the emulsion.